2021 Toyota Highlander LE V6 anti-theft stop working

I can no longer lock or unlock the doors using the key fob. I replaced the battery in both key fobs and checked all related fuses, including the horn fuse, and they are working fine.

Currently, I have to manually lock and unlock the car by inserting the key into the driver’s side door. I can start the car without any issue after unlocking the door with a key insert.

When I press the key fob buttons, the car does not respond at all, with no door lock or unlock, and no flashing lights like it used to.

Do I need to replace the alarm ECU, or could a faulty alarm sensor be causing this issue? Do I just replace the alarm system?

Thank you in advance for your help on this matter!

Did you replace them the correct way? Some batteries are 1.5v, 3v, and some are even 6v. Did you get the correct battery? It seems odd that the light on the fob doesn’t work after replacing the batteries.

Make sure the remotes work before worrying about the car. Technicians have checklists so they don’t jump to conclusions. Maybe let someone look at it instead of guessing.

@Pierce
Thank you for your response. I replaced them with new Duracell 20163V batteries in both key fobs, but there is no light on either fob.

I agree. I was hoping someone else had faced a similar situation. If I don’t get useful suggestions, I’ll take it to a technician.

@Davi
My 2020 uses a 2032 battery in the key fob. Try those.

Check if the fob light flashes red when you press the buttons.

Can you lock/unlock all doors from the driver side interior button? If not, check the D/L fuse in the interior fuse box. Use a multimeter to check, as they can blow but still look okay. This might be a door lock issue and not a wireless fob issue or anti-theft issue.

You need to dig deeper; don’t buy modules just yet.

My 2020 uses 2032 batteries.

Disconnect your battery for 15-20 minutes, then reconnect it and see what happens.